What happens to old and faulty solar panels? Common faults, UK recycling rules and what to do

Solar panels last 25 years or more, inverters do not, and none of it goes in the skip. How panels fail, how to spot a problem from the inverter, what the UK WEEE rules say and where old panels actually go.

For home By suj · · 8 min read · 1,750 words

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A great many UK domestic solar systems are now old enough for the inverter to be reaching the end of its life, and a question we hear more and more from customers is some version of "the inverter has died — what happens now, and can I even throw the old panels away?"

The short answers: the panels are probably fine and the inverter probably is not; a failed panel is electrical waste and cannot go in a skip; and there are free routes for getting rid of it. The evidence is below.

How long panels and inverters actually last

Panels are the durable part. The Energy Saving Trust puts it plainly: "Your solar panels should last 25 years or more." The inverter — the box that turns the panels' DC output into mains AC — is a different story: the same guidance says you "need to replace this after around 12 years", with warranties starting at five years and often extendable to 15 (Energy Saving Trust, n.d.). Budget for at least one inverter in the life of the panels.

The IRENA and IEA-PVPS end-of-life study models panels on a "30-year average panel lifetime" and groups failures into three phases: infant failures in the first four years, mid-life failures from years five to eleven, and wear-out failures from year twelve onwards (IRENA and IEA-PVPS, 2016). The likely fault changes with age.

The common faults, and when they show up

The IEA-PVPS review of module failures is the best single catalogue of what goes wrong (IEA-PVPS, 2014).

  • Early life: about 5% of failure cases came from damage in transit, and the typical infant failures are junction-box faults, glass breakage, defective cell interconnects, loose frames and delamination.
  • Mid-life: at around eight years, one study found defective interconnections and glass breakage leading, with junction boxes and cables (12%), burn marks on cells (10%) and encapsulant failure (9%) behind them.
  • Wear-out: past fifteen years, the dominant failures are delamination, cells electrically isolated by cracks, and discolouring of the laminate, with power losses "between 0% and 20%, in the mean 10%".

Four terms come up repeatedly:

Microcracks are fractures in the silicon cell from mechanical stress — vibration in transit, a knee on the panel during installation, snow load, years of thermal cycling. Most are invisible without electroluminescence imaging. A cracked region can become electrically isolated, so the power loss arrives in steps (IEA-PVPS, 2014).

Hot spots are localised heating where a shaded, cracked or shunted cell has to dissipate the current from the rest of the string. The review reports differences of "multiples of 10 K" between a hot spot and its neighbours, and classes it as a failure that may cause fire if a follow-up failure occurs (IEA-PVPS, 2014). Do not leave this one to "see how it goes".

Potential-induced degradation (PID) happens when high voltage between the cells and the earthed frame drives ions through the module, creating large shunts. Power drops, and low-light performance suffers most — a PID-affected system looks worst in a British winter (IEA-PVPS, 2014).

Delamination and discolouration are the slow ones: the encapsulant separating from glass or cells, or turning yellow then brown as moisture and heat get to it. A cell that runs hotter than its neighbours browns faster, so a mottled panel is a clue, not a blemish (IEA-PVPS, 2014).

Table 1. Components of a domestic solar PV system: typical lifespan, common faults and what to do. Sources: Energy Saving Trust (n.d.); IRENA and IEA-PVPS (2016); IEA-PVPS (2014); PV CYCLE UK (n.d.).
ComponentTypical lifespanCommon faultWhat to do
Panels (modules)25 years or more; 30-year average in end-of-life modellingMicrocracks, hot spots, PID, delamination, discolouration, glass breakageCompare output with earlier years; if it has stepped down, ask the installer to inspect with thermal or electroluminescence imaging
InverterAround 12 years; warranties from 5 years, extendable to 15Complete failure, error codes, overheatingCheck the display or app; zero on a sunny day is the classic sign. Replace under warranty if in date
Junction boxes and cablesLife of the panel, but a leading mid-life failureCorrosion from moisture ingress, loose connections, failed bypass diodesDo not open a junction box yourself; isolate at the DC switch and call the installer
Failed panel or inverter—Disposal, not a faultIt is WEEE: installer take-back or a PV CYCLE UK collection point, never the skip

Spotting underperformance from the inverter

You do not need test equipment to catch most problems early; you need a baseline and a habit. The inverter's display or app shows power now and energy generated today, this month and this year. The Energy Saving Trust notes that some inverters have "online monitoring functions and warn you by email if the system fails", and that your installer should have left written details of the checks you should make (Energy Saving Trust, n.d.). Turn alerts on if you can: most dead inverters we see had been dead for months before the electricity bill gave it away.

Beyond alerts, three checks are enough:

  1. Zero on a bright day means the inverter or a switch, not the panels. Check the DC isolator and the AC breaker before calling anyone.
  2. Same month, different year. If this June generated far less than June two years ago and nothing has changed on the roof, something has changed in the system. A step down that stays down points to a panel or string fault; a slow slide is ageing.
  3. A photograph a year, from the garden on a clear day. Discolouration, a browning cell or a cracked pane show up on a phone camera long before they show in the numbers.

The UK rules: solar panels are WEEE

Under the Waste Electrical and Electronic Equipment Regulations 2013, a solar panel is electrical equipment like a fridge. The Environment Agency's guidance lists "PV (photovoltaic) panels (solar panels)" as category 14 of the regulated equipment, with an unusual rule: because panels are "of a generic size and design they must be reported as household (B2C (business to consumer)) regardless of where they're installed" — even on a solar farm (Environment Agency, 2025).

So the companies that put panels on the UK market must finance their collection and treatment, through a producer compliance scheme, and there is a national collection target. Defra set the 2026 household PV panel target at 1,845 tonnes, against 1,677 tonnes actually collected in 2025, and cites research forecasting 13,879 tonnes needing treatment by 2030 (Defra, 2026). Small numbers beside the 532,882-tonne overall household WEEE target, but the 2030 forecast is more than eight times last year's collections.

Where old panels go, and what is recovered

PV CYCLE began as the European industry's voluntary take-back initiative in the early 2000s (IRENA and IEA-PVPS, 2016). Its UK arm is an accredited producer compliance scheme under the 2013 Regulations and runs collection points for anyone with fewer than 30 panels — every domestic system — plus a collection service for larger quantities (PV CYCLE UK, n.d.). The other route is whoever fits the replacement: ask them to take the old unit away, and ask where it will go.

What comes out of a recycled panel is mostly glass. A typical crystalline-silicon panel is about 76% glass, 10% polymer, 8% aluminium, 5% silicon, 1% copper and under 0.1% silver (IRENA and IEA-PVPS, 2016). The frame comes off easily and is worth money; the glass is the bulk; the silicon and silver are the valuable part but the hardest to reach, laminated between glass and polymer.

That laminate is the recycling problem. The current IEA-PVPS status report describes three steps — delamination, metal recovery and preparing the materials for market — with newer delamination methods using diamond wire, water jets and infrared lamps to separate the layers rather than shredding everything, and chemical processes to recover the metals (IEA-PVPS, 2025). For scale, 48,395 tonnes of panel waste were collected across 18 European countries in 2022.

The prize is real. IRENA and IEA-PVPS projected cumulative panel waste of 1.7 to 8 million tonnes globally by 2030 and 60 to 78 million tonnes by 2050, depending on how early panels are replaced, with recoverable raw materials worth around USD 450 million by 2030 and USD 15 billion by 2050 (IRENA and IEA-PVPS, 2016).

What to do when something fails

  1. Look at the inverter first. Note any error code, photograph the display, check the isolators. Do not open anything.
  2. Contact your installer. MCS advises contacting the installer first and allowing a reasonable time to respond, with 14 days as a sensible maximum (MCS, n.d.). Keep the MCS certificate and the warranties together.
  3. If the installer has gone or will not help, MCS runs a complaints process and, for contracts under its redeveloped scheme, a free dispute resolution service whose decisions are binding on the installer (MCS, n.d.).
  4. For disposal, use the installer or a PV CYCLE UK collection point. A failed inverter is WEEE too. Nothing goes in the skip.
  5. Before replacing panels because "they are old", get the output history. A fifteen-year-old system running 10% down is behaving as the research says it should.

We do not install solar, but our home support visits increasingly include getting an inverter's monitoring app working, or pulling years of generation data into a spreadsheet so a householder can see what is happening on the roof. If that would help, get in touch.

Sources

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